Function for flattening nested array

flatten.js

/**
 * Flatten nested array
 * @param {Array} array Nested array
 * @return {Array} Flat array
 */
function flatten(array) {
  return array.reduce(function (flat, toFlatten) {
  	// if current item is array flatten it, otherwise concatenate value to processed flat array
    return flat.concat(Array.isArray(toFlatten) ? flatten(toFlatten) : toFlatten);
  }, []);
}